Ok, maybe not a network issue then. It was failing to call an AVTransport service function, but was not failing other service functions.
0095021: 348: Reader: CWinINetReader::Open: Start
0095021: 348: Reader: CWinINetReader::Open: Opening
http://192.168.0.71:4444/dri/tuner0/AVTransport0095021: 3664: Reader: CWinINetReader::Thread: Start
0095021: 3664: Reader: CWinINetReader::Connect: Start
0095021: 3664: Reader: CWinINetReader::Connect: Finish (0 ms)
0095021: 3664: Reader: CWinINetReader::DownloadFromHTTPURL: Start
0095021: 3664: Reader: CWinINetReader::DownloadFromHTTPURL: Failed (header status code: 500)
0095021: 3664: Reader: CWinINetReader::DownloadFromHTTPURL: Success
0095021: 3664: Reader: CWinINetReader::DownloadFromHTTPURL: Finish (0 ms)
0095021: 3664: Reader: CWinINetReader::Thread: Finish (0 ms)
0095021: 348: Reader: CWinINetReader::Open: Finish (0 ms)
0095021: 348: Reader: CWinINetReader::Close: Start
0095021: 348: Reader: CWinINetReader::Close: Finish (0 ms)
0095021: 348: Sharing Plugins: CDLNADeviceConnectionStatus::NotifyCommunicatedWithDevice: Error communicating with device: HDHomeRun Prime Tuner 13173CA6-0